The invention relates to a heat exchanger, particularly for heat pumps, comprising a secondary part which comprises at least one helically coiled pipe which contains a refrigerant, and a primary part which surrounds the secondary part and serves for the flow of a heat carrying medium.
Heat exchangers of a similar type are known in various forms (for example Swedish patent specification No. 196,760, U.S. Pat. No. 3,526,273 and U.S. Pat. No. 3,163,210). For heat pump installations, two heat exchangers are normally used, namely firstly an evaporator in which the heat carrying medium of a heat source circuit transfers its heat to a refrigerant circuit, and secondly a condenser in which the refrigerant circuit again transfers its heat to a heat carrying medium in a heat delivering circuit. In these two heat exchangers it is desirable to achieve the greatest possible heat transfer and the smallest possible pressure loss.
The possibilities of improving the heat transfer will be understood from the following equation: EQU Q=k.multidot.F.multidot..DELTA.t.
All methods of improving the heat transfer factor Q are aimed at optimizing one or all of these influencing factors. In heat pump installations there are certain limits to the increase of the temperature difference .DELTA.t, as it only can be increased at the expense of the output of the compressor, whereby the total output of the heat pump installation is reduced. Improvements in the heat transfer figure "k" can only be achieved by influencing the flow conditions and by choice of materials. Furthermore it is generally known to make the heat exchanger surface "F" as large as possible by constructive measures, e.g. by fixing fins or the like. The helical coiling of the pipes also serves this purpose. However, limitation will often be set by the space requirements of the heat exchanger.